Modular vascular prosthesis and methods of use

ABSTRACT

The present invention relates a vascular prosthesis and related assembly methods that includes a plurality of modular segments inter-engaged by flexible, and preferably lockable, inter-engageable elements forming joints or other connector areas. The segments may have a number of different mechanical properties and may be assembled by the clinician, through mechanical or chemical joining, to customize the prosthesis for a specific patient or application.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 11/962,463, filed on Dec. 21, 2007, which is a continuation-in-partof U.S. patent application Ser. No. 11/067,090, filed on Feb. 25, 2005,now U.S. Pat. No. 8,002,818, the disclosures of which are herebyincorporated by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to modular vascular prostheses, such asstents, and related methods of use. More particularly, the presentinvention relates to vascular prostheses having a modular constructionthat permits the properties and length of the prosthesis to becustomized for a specific patient.

BACKGROUND OF THE INVENTION

Numerous stent designs are known in the art, of which self-expanding andballoon-expandable stents are the predominant commercially availabletypes. Self-expanding stents, such as the stents described in U.S. Pat.No. 4,580,568 to Gianturco, generally provide good crush-resistance andaxially flexibility, thus permitting delivery through tortuous anatomy,but provide lower radial strength once deployed. Balloon-expandablestents, such as the stents typified by U.S. Pat. No. 4,739,762 toPalmaz, provide high radial strength, but tend to have increased axialrigidity that affects deliverability through tortuous vessels. It hastherefore been a goal of many expandable stent designs to enhance axialflexibility of the stent to improve deliverability, and thus the numberof potential applications for the device, while retaining an acceptablelevel of radial strength.

Previously known stents are generally supplied in a variety of lengthsand diameters, so the clinician can select the stent most appropriatefor a specific patient. Such stents typically have homogeneousproperties along the length of the stent and provide limited options forcustomization responsive to the needs of a particular patient.

In certain applications, the best solution for a particular patientwould involve a combination of the mechanical and operating propertiesof both balloon-expandable and self-expanding stents. Therefore, itwould be desirable to provide a modular stent that permits the clinicianto “mix and match” stent modules to build a stent having specificcharacteristics tailored for a specific patient or application.

For example, it may be desirable to provide a stent having axial modulesof variable rigidity and crush-resistance, such as for use in thecarotid arteries. Due to the generally exposed nature of these arteriesin the region of the neck, situations have been reported whereballoon-expandable stents have been subjected to partial crushing. Onthe other hand, self-expanding stents are susceptible to migration.Therefore, it would be desirable in certain applications to provide astent having a resilient, self-expanding central portion andballoon-expandable end regions that permit the stent to be anchored inposition.

The ability to vary the mechanical properties of the stent also wouldpermit a stent to include non-metallic components, such as biodegradableor bioabsorbable segments. This ability might prove particularlyadvantageous where it is desired to deliver a predetermined dose of drugto via drug-eluting segments, for example, by incorporating a specifiednumber of drug-eluting segments into the prosthesis that eventuallydissolve in the fluid stream through the vessel.

As yet another example, U.S. Pat. No. 6,048,361 to Von Oepen describes astent designed for use in bifurcated vessels having a side branchaperture. As described in that patent, the stent is manufactured withfixed length regions proximal and distal to the aperture. Thus, thestent may not be suitable in some patients because the fixed length ofthe proximal or distal region may interfere with collateral vesselsupstream or downstream of the bifurcation. Accordingly, it would bedesirable to provide a vascular prosthesis that includes a side branchaperture, but which has proximal and distal regions that may be tailoredfor a specific patient.

U.S. Pat. No. 5,824,037 to Fogarty et al. describes a modularintralumenal prosthesis, such as for a stent-graft, that includes aplurality of modules having standard interface ends for engagingadjacent modules. The modules employed in the prosthesis may includevariations in axial length, cross-section, perimeter, resilientexpansive force and axial flexibility. The modules are “locked” togetherby stitching a liner material.

One drawback of the prosthesis described in the Fogarty et al. patent isthat the prosthesis may lack structural rigidity in the expandedconfiguration. In particular, the patent describes no mechanism topositively engage the modules other than the liner material. Ittherefore would be desirable to provide a modular stent wherein themodules cannot be locked together without stitching or a liner material.

The foregoing patent also does not teach that a modular stent may beused to improve conformance of the stent to a patient's vasculature whenused in a bifurcated region, or the desirability of intermixing segmentsincluding different materials, including bioabsorbable or drug-elutingsegments.

Therefore, it would be desirable to provide a vascular prosthesisincluding a plurality of modular segments interconnected by lockablejoints that enhance articulation between adjacent segments duringdelivery of the prosthesis and enhance structural rigidity of theprosthesis in the deployed configuration.

It also would be desirable to provide a vascular prosthesis thatincludes a plurality of modular segments interconnected by a pluralityof joints, in which the modular segments include different materials orstrut configurations, thereby permitting the structural rigidity of thevascular prosthesis in the deployed configuration to be tailored for aspecific patient or application.

It further would be desirable to provide a vascular prosthesis includinga plurality of modular segments, wherein one or more segments may bebioabsorbable or drug-eluting, to provide predetermined doses of drug tothe vessel wall or intravascularly to a desired tissue region.

Still further, it would be desirable to provide a vascular prosthesisthat includes a plurality of modular segments, wherein one or moresegments of customizable length may be intermixed to provide a desiredfeature, for example for the treatment of bifurcated vessels oraneurysms.

Still further, it would be desirable to provide a method for assemblinga device wherein a physician could intermix device components formed ofone or more interlocking modular segments, in order to provide avascular prosthesis with radial force and structural rigidity tailoredto a specific patient or application.

Still further, it would be desirable to provide a method for assemblinga device wherein a physician could intermix device components thatinclude one or more interlocking modular segments to make a customizablevascular prosthesis by snapping the components together without the needfor assembly tools.

Still further, it would be desirable to provide a system for assemblinga device that

includes interlocking modular segments and interlocking modular endsegments that can be joined to form a device having a customizablelength, configuration or structural rigidity.

It also would be desirable to provide device components that includemodular segments configured to be welded together, so to eliminate theneed for traditional laser cutting of long tubular members.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a vascular prosthesis that includes a plurality of modularsegments interconnected by a plurality of inter-engageable elementsforming joints, which enhance articulation between adjacent segmentsduring delivery of the prosthesis and enhance structural rigidity of theprosthesis in the deployed configuration.

It is also an object of this invention to provide a vascular prosthesisthat includes a plurality of modular segments interconnected by joints,wherein the modular segments are made with different materials or strutconfigurations and permit permitting the structural rigidity of thevascular prosthesis in the deployed configuration to be tailored for aspecific patient or application.

It is another object of the present invention to provide a vascularprosthesis that includes a plurality of modular segments, one or moresegments of which may be bioabsorbable or drug-eluting and providepredetermined doses of drug to the vessel wall or intravascularly to adesired tissue region.

It is a further object of the present invention to provide a vascularprosthesis that includes a plurality of modular segments, one or moresegments of which may be intermixed to provide a desired feature and tohave proximal and distal regions of customizable length, for example forthe treatment of bifurcated vessels or aneurysms.

Still further, it is an object of the present invention to provide amethod for assembling a device, by which a physician can intermix devicecomponents that include one or more interlocking modular segments, so toprovide a vascular prosthesis with structural rigidity tailored to aspecific patient or application.

Still further, it is an object of the present invention to provide amethod for assembling a device, by which a physician can intermix devicecomponents that include one or more interlocking modular segments, so toprovide a vascular prosthesis with variable radial force and/or variablestructural rigidity, for example, for the treatment of plaque in bloodvessels.

Still further, it is an object of the present invention to provide asystem for assembling a device, by which interlocking modular segmentsand interlocking modular end segments can be joined to form a prosthesisof customizable length, configuration or structural rigidity.

Still further, it is an object of the present invention to provide amethod for assembling a device which eliminates the need for lasercutting and processing different length devices by providinginterlocking modular segments that a physician can intermix to form acustomizable length device.

Still further, it is an object of the present invention to provide amethod for assembling a device wherein a physician can intermix devicecomponents that include one or more interlocking modular segments tomake a customizable vascular prosthesis by snapping the componentstogether without the need for assembly tools.

Still further, it is an object of the present invention to providemodular segments configured to be welded together to eliminate the needfor traditional laser cutting and expansion techniques of longer tubes,which have a disproportionately high scrap rate for longer stents andsmaller stents.

These and other objects of the present invention are accomplished byproviding a vascular prosthesis having a delivery configuration and anexpanded configuration. The prosthesis includes a plurality of modularsegments interengaged by flexible, and preferably lockable,inter-engageable elements that form joints. In accordance with theprinciples of the present invention, the segments may have a number ofdifferent characteristics and may be assembled by the clinician tocustomize the prosthesis for a specific patient or application.

For example, segments may have differing mechanical properties and maybe self-expanding or balloon-expandable, and may include differing strutconfigurations and/or different materials, such as metal alloys orbioabsorbable or drug-eluting polymers. In addition, individual segmentsof the vascular prosthesis may include specific features, such as aside-branch aperture for bifurcated vessels or a covering for excludingan aneurysm.

In one embodiment, the inter-engageable element used to join the modularsegments include ball and socket joints that facilitate articulationbetween adjacent segments during delivery of the stent through tortuousanatomy. Each segment includes proximal and distal ends, wherein eachend includes a plurality of ball elements, socket elements or acombination of ball and socket elements, depending upon the mechanicalproperties, strut configuration and intended purpose of a given segment.For example, where a segment includes a hoop having a plurality ofgenerally zig-zag struts, the ball and socket elements may be formed onextensions of the struts of adjacent segments.

In an alternative embodiment, the inter-engageable elements used to jointhe interlocking modular segments include a substantially ring shapedmale interface element and a rounded female interface element. Eachsegment includes struts and bends. Each segment also has a proximal endand a distal end, wherein each end includes a plurality of ring shapedmale interface elements, rounded female interface elements, or acombination of male and female interface elements, depending upon themechanical properties, strut configuration and intended purpose of agiven segment. The ring shaped male interface element and rounded femaleinterface element can be joined and locked so the interlocking modularsegments are joined to form a prosthesis having a customizable length,configuration or structural rigidity.

In another alternative embodiment, the modular segments include weldingzones in

the connector areas. The modular segments of this embodiment include azig-zag configuration of struts and bends. The welding zones include arounded protrusion formed at the end of one or more selected bends onone side of a segment and tongs at the end of one or more selected bendson the opposite side of the segment. The rounded protrusions of onesegment join and inter-engage with the tongs on an adjoining segment atthe connector areas of the device components.

In still another alternative embodiment, the inter-engageable elementsused to join the modular segments include intertwined spiral elementsthat facilitate articulation between adjacent segments during deliveryof the stent through tortuous anatomy. Each segment includes proximaland distal ends, wherein each end includes a spiral element thatinterengages a spiral element of an adjacent segment. The spiralelements have a common orientation, either clockwise orcounterclockwise, depending upon the mechanical properties, strutconfiguration and intended purpose of a given segment. Each segmentillustratively may include a hoop having a plurality of generallyzig-zag struts, wherein the spiral elements extend may be formed onextensions of the struts of at regular intervals.

In accordance with a preferred aspect of the present invention,interconnected joints are configured to lock when the prosthesis istransitioned from the delivery configuration to the deployedconfiguration. For example, the socket elements may include apliers-like element that closes to grip the ball elements when thesegment is deployed, thereby preventing adjacent segments fromdisengaging in the deployed configuration. In the alternativeembodiment, the interference of the interconnected spiral elements mayincrease, thereby locking the spiral elements together.

In alternative embodiments of the prosthesis of the present invention,axial flexibility of the prosthesis may be further enhanced byincorporating flexible, physical connections between the strutscontained within a given segment.

Delivery systems for delivering the inventive prostheses of the presentinvention also are provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects of the invention will be apparent uponconsideration of the following detailed description, taken inconjunction with the accompanying drawings, in which like referencecharacters refer to like parts throughout, and in which:

FIG. 1 is a plan view of an exemplary modular vascular prosthesisconstructed in accordance with the principles of the present inventionthat has been cut along line A-A and flattened;

FIGS. 2A and 2B are, respectively, perspective views of the modularvascular prosthesis of FIG. 1 disposed in the delivery configurationaround a balloon catheter and in the deployed configuration;

FIG. 3 is a side view of the vascular prosthesis of FIG. 1 whereinalternating segments include different materials;

FIG. 4 is a side view of the vascular prosthesis of FIG. 1 wherein eachsegment includes additional flexible interconnections;

FIG. 5 is a side view of a prosthesis constructed in accordance with thepresent invention wherein one segment includes a portion defining aside-branch aperture;

FIG. 6 is a side view of a prosthesis constructed in accordance with thepresent invention wherein one segment includes a graft covering for usein excluding an aneurysm;

FIG. 7 is a side view of an alternative embodiment of the prosthesis ofthe present invention wherein alternating modular segments includeeither all ball elements or all socket elements;

FIG. 8 is a side view of an alternative embodiment of the prosthesis ofthe present invention wherein each segment that combines both ball andsocket elements at each end;

FIGS. 9A and 9B are, respectively, side views of a locking ball andsocket joint of the present invention depicted in the deliveryconfiguration and the deployed configuration;

FIG. 10 is a perspective view of further alternative ball and socketjoint that permits self-expanding segments and balloon-expandablesegments to be intermixed;

FIG. 11 is a plan view of an embodiment of a modular vascular prosthesisof the present invention that has been cut along line A-A and flattenedin which the interconnected joints include intertwined spiral elements;

FIGS. 12A and 12B are, respectively, perspective views of the modularvascular prosthesis of FIG. 11 disposed in the delivery configurationaround a balloon catheter and in the deployed configuration;

FIG. 13 is a detailed view of the intertwined spiral elements of theembodiment of FIG. 11;

FIG. 14A-14C are, respectively, views of a marker opening andradio-opaque rivet as may be applied on the end loops of the prosthesesdepicted in FIGS. 1 and 11;

FIG. 15 is an alternative arrangement for providing radio-opaque markerson the prosthesis of the present invention;

FIG. 16 is another alternative arrangement for providing radio-opaquemarkers on the prosthesis of the present invention;

FIG. 17 is an illustrative delivery system for use in delivering theprosthesis of the present invention;

FIG. 18 is a plan view of an alternative ring-shaped male interfaceelement and a rounded female interface element that permits joining andintermixing of interlocking modular segments;

FIG. 19 is a side view of an interlocking modular segment as seen fromboth the proximal and distal ends of an interlocking modular segment;

FIG. 20 is a detail view of an interlocking modular segment in anembodiment of the invention;

FIG. 21 is a detail view of the first end of an interlocking modularsegment in an embodiment of FIG. 20;

FIG. 22 is a plan view of the second end of an interlocking modularsegment in an embodiment of FIG. 20;

FIG. 23 is a plan view of a section of a modular vascular prosthesisassembled using methods and systems of the present invention;

FIG. 24A, 24B and 24C are, respectively, a figure sequence illustratinga method of assembling the modular vascular prosthesis of FIG. 23, andplan and perspective views of the modular vascular prosthesis of FIG. 23disposed in the delivery configuration around a balloon catheter and inthe deployed configuration;

FIG. 25 is a perspective view of the vascular prosthesis of FIG. 23wherein alternating groups of segments include material of relativeradial strength and weakness; and

FIG. 26 is a plan view of modular segments that have been weldedtogether and include welding zones at the connector areas.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a first family of embodiments of a vascularprosthesis of the present invention is described. Vascular prosthesis10, for example, a stent, is shown cut along line A-A along itslongitudinal axis and flattened into a plane for illustrative purposes.Vascular prosthesis 10 includes a tube-like structure made up of aplurality of interconnected modular segments, including inner segments11 and end segments 12. In the illustrated embodiment, segments 11 and12 include a plurality of struts 13 joined at the ends by bends 14 toform a generally zig-zag configuration in the deployed configuration. Aswould be understood by one of ordinary skill in the art, segments 11 and12 may include many alternative strut configurations without departingfrom the scope of the present invention.

In accordance with the principles of the present invention, joints 15interconnect segments 11 and 12. In a first preferred embodiment, eachjoint 15 includes ball element 16 engaged within socket element 17.Inner segments 11 include ball elements 16 and socket elements 17 ateither end, while end segments 12 include such elements on only one end.Ball elements 16 and socket elements 17 preferably are formed asextensions on selected bends 14 disposed between struts 13 around thecircumference of the stent.

In FIG. 1, ball elements 16 are disposed on one end of each innersegment 11 while socket elements 17 are disposed on the other end of thesegment. Adjacent ball or socket elements are depicted as having oneintervening bend 14 around the circumference of the stent, but mayinclude two or more intervening bends. Joints 15 permit a significantdegree of articulation between adjacent segments, particularly in thedelivery configuration, making the stent highly flexible and thus ableto negotiate tortuous anatomy. Although ball elements illustratively areshown as substantially circular structures, ball elements 16 and thecorresponding sockets may have other suitable shapes, such as ovals,polygons or diamonds.

The zig-zag configuration of struts 13 and bends 14 depicted in FIG. 1preferably is

formed by laser cutting a solid tube. Vascular prosthesis 10 preferablyis flexible enough to conform to the shape of a delicate vessel withoutsubstantially remodeling the vessel. In particular, the zig-zagconfiguration of segments 11 and 12 is expected to conform to a naturalcurvature of a vessel wall. Of course, other patterns of struts andbends, such as are known in the art, advantageously be used withinsegments 11 and 12.

Referring to FIG. 2A, vascular prosthesis 10 includes a balloonexpandable material and is shown crimped in a contracted deliveryconfiguration over balloon 20 of balloon catheter 22. This may beaccomplished by assembling a desired number of inner segments 11 betweenend segments 12 to provide a stent of a desired length, and theassembled stent may then be crimped onto balloon 20 using any of anumber of previously-known crimping devices. Because the stent isretained centered on balloon 20, ball elements 16 and socket elements 17remain in engagement to form a substantially smooth exterior surface ofthe stent.

Balloon catheter 22 is delivered transluminally to a target site withina patient's vessel using, for example, well-known percutaneoustechniques. Vascular prosthesis 10 or portions of catheter 22 may beradiopaque to facilitate positioning within the vessel. The target sitemay, for example, include a stenosed region of the vessel at which anangioplasty procedure has been conducted. In accordance with the presentinvention, joints 15 permit vascular prosthesis 10 to flex along itslength to negotiate tortuous anatomy.

Referring to FIG. 2B, balloon 20 is inflated to expand vascularprosthesis 10 to the deployed configuration in which it engages andsupports the wall of the vessel at the target site. As shown in FIG. 2B,ball elements 16 continue to be retained in the socket elements 17 whensegments 11 and 12 are radially expanded. Balloon 20 is then deflatedand balloon catheter 22 is removed from the vessel, leaving vascularprosthesis 10 supporting the vessel. The web structure of vascularprosthesis 10 provides sufficient radial stiffness to maintain vascularprosthesis 10 in the expanded configuration, with minimal recoil.Vascular prosthesis 10 optionally may include an external coatingconfigured to inhibit restenosis.

Referring to FIG. 3, in accordance with one aspect of the presentinvention, inner

segments 11 may include different materials, strut configurations, ortypes of radially expandable segments that are selectively intermixed tocustomize the vascular prosthesis for a specific patient or application.Segments also may include side-branch apertures for use in treatingbifurcated vessels, graft covered segments for excluding aneurysms anddrug-eluting segments that are pre-loaded with a predetermined amount ofdrug and may be assembled to provide a desired dose.

For example, whereas metallic radially expandable inner segments provideincreased radial stiffness in the deployed configuration, bioabsorbableor drug-eluting radially expandable segments may be better suited fordrug delivery. In the embodiment of FIG. 3, vascular prosthesis 30includes five metallic segments 31 alternating with five drug-elutingsegments 32, all disposed between end segments 33. In a preferredembodiment, the drug may include a tetrazole-containing rapamycin foruse in treating restenosis, such as described in U.S. Pat. No. 6,015,815to Mollison, which is incorporated herein by reference in its entirety.

Alternatively, because joints 34 include ball elements 35 and socketelements 36 that are common for segments 31, 32 and 33, the segments maybe assembled in any order desired for a specific patient or application.Thus, for example, segments 32 and 33 may be reordered so that the fivemetallic segments are at one end of the stent, and the five polymericsegments are at the other end. Of course, as would be appreciated bythose of skill in the art, many other combinations of materials arepossible without departing from the scope of the invention.

Referring to FIG. 4, in accordance with a further embodiment of thepresent invention, vascular prosthesis 40 includes a plurality of innersegments 41 disposed between end segments 42. Each inner segment 41illustratively includes two zig-zag hoops 43 coupled by spiral joints 44to further increase the longitudinal flexibility of the segment.Segments 41 further include joints 45 including ball elements 46 andsocket elements 47 that enable the segment to be coupled to adjacentsegments 41 and end segments 42 to assemble the stent to a desiredlength. As for the previous embodiments, joints 45 also enhanceflexibility of the stent during transluminal insertion.

Referring to FIG. 5, an alternative embodiment of vascular prosthesis 40suitable for use in a bifurcated vessel is described. As notedhereinabove, stents having side-branch openings are known in the art,such as described in the aforementioned Von Oepen patent. One of thedifficulties of such previously-known stents is that the regionsproximal and distal to the side-branch opening are fixed at the time ofmanufacture and may be unsuitable for a particular patient. For example,the proximal or distal region may partially occlude collateral vessels.

Stent 50 of FIG. 5 solves this foregoing problem by permitting theclinician to tailor the lengths of the proximal and distal regions asdesired for a specific patient or application. In particular, stent 50includes inner segments 41 and end segments 42 as depicted in FIG. 4,where each segment 41 and 42 further includes hoops 43 coupled by spiraljoints 44 and ball and socket elements 45 and 46, respectively. Inaddition, stent 50 includes inner segment 51 including hoops 52 coupledby spiral joints 53 and defining side-branch aperture 54.

Illustratively, stent 50 includes single segment 41 coupled on eitherside, however, it is to be understood that any number of segments 41could be coupled on either side of inner segment 51. In addition, morethan one inner segment 51 may be employed, with the side-branchapertures 54 disposed at different circumferential orientations, therebyenabling access to multiple side branch vessels. Accordingly, thevascular prosthesis of the present invention may be assembled by theclinician to match the anatomy of a specific patient's vasculatureshortly before implantation and inner segments of various lengths andconfigurations may be intermixed as necessary to match the patient'svasculature.

With respect to FIG. 6, a further alternative embodiment of the vascularprosthesis of the present invention is described for use in excluding ananeurysm. Stent 60 is similar in design to the stent of FIG. 1, exceptthat it includes a graft covered segment. More particularly, stent 60includes a plurality of inner segments 11 interposed between endsegments 12. Each of inner segments 11 includes ball and socket elements16 and 17, respectively, that engage a corresponding element on anadjacent segment to form joints 15.

Stent 60 further includes inner segment 61, illustratively having aconfiguration similar to that of segment 41 of FIG. 4. In particular,segment 61 includes zig-zag hoops 62 coupled by spiral joints 63, withthe outermost hoops including ball elements 64 and socket elements 65that engage the adjacent segments. In accordance with this aspect of thepresent invention, segment 61 includes graft covering, such as Dacron orexpanded polytetrafluoroethylene (ePTFE), affixed to its outer surfaceby a biocompatible adhesive or sutures. In this manner, stent 60 may beassembled to include one or more segments 61 to exclude an aneurysmwithin a vessel, yet continue to permit blood flow to reach healthyvessel wall upstream and downstream of the aneurysm.

Referring to FIG. 7, a further alternative embodiment of the vascularprosthesis of the present invention is described. Vascular prosthesis 70includes inner segments 71, inner segments 72 and end segments 73 and74. Each segment 71-74 includes a plurality of struts joined by bends toform zig-zag hoops. Whereas inner segments 11 of the embodiment of FIG.1 included ball elements at one end and socket elements at the other,segments 71 include only ball elements at either end and segments 72include only socket elements at either end. End segment 73 includes onlyball elements at one end and end segment 74 includes only socketelements at one end. As will be understood, segments 71 and 72 mayinclude the same or different strut configurations, may be of the sameor different lengths or may have the same or different mechanicalproperties.

Referring now to FIG. 8, a still further alternative embodiment of thevascular prosthesis of the present invention is described. Vascularprosthesis 80 is similar in construction to stent 40 of FIG. 4, andincludes inner segments 81 and end segments 82. Unlike inner segments41, which included only ball elements at one end and socket elements atthe other, segments 81 have ball elements 83 alternating with socketelements 84 around the circumference of the segment at either end.

As for the previous embodiments, segments 81 may have the same ordifferent strut configuration, the same or different lengths or the sameor different mechanical properties.

With respect to FIGS. 9A and 9B, in accordance with a further aspect ofthe invention, locking joints suitable for use in the vascularprostheses of FIGS. 1-8 are described. Ball elements 91 and socketelements 92 of FIG. 9 are designed to add structural rigidity to joints93 of a vascular prosthesis in the deployed configuration. Inparticular, as zig-zag segments 94 expand from the deliveryconfiguration (FIG. 9A) to the expanded deployed configuration (FIG.9B), socket element 92 functions as pliers that partially closes aroundball element 91, thereby fixedly engaging the ball element and enhancingthe structural rigidity of the assembled prosthesis.

To facilitate this pliers-like action of socket elements 92, bends 95preferably include reduced thickness regions, thereby facilitatingexpansion of the segments into the deployed configuration. Providingthinner bends 95 also promotes closing of socket element 92 around ballelement 91 as the arms of the socket element are forced together duringexpansion of the vascular prosthesis, as depicted in FIG. 9B.Advantageously, the closing action of socket element 92 about ballelement 91 reduced the risk of disengagement of adjacent segments ofvascular prosthesis in the deployed configuration.

With respect to FIG. 10, a further embodiment of a ball and socket jointsuitable for

use with vascular prosthesis of the present invention is described. Inthe preceding embodiments the socket elements generally are of uniformthickness. In FIG. 10, however, joint 100 includes socket element 101has a thickness equal to about have of strut thickness 102 and ballelement 103 including flange 104, wherein the flange also has athickness of about one-half strut thickness 105. When coupled together,ball element 103 projects into socket element 101, while flange 104bears against the underside of socket element 101. In this manner, ballelement 103 is free to articulate within socket element 101, but flange104 prevents ball element 103 from passing entirely through the socketelement.

Joint embodiment of FIG. 10 may be particularly advantageous when usedin conjunction with the stent of FIG. 7, especially where the innersegments 71 and 72 are selected to have different radial expansionproperties, e.g., such as resilient self-expanding segments and rigidballoon-expandable segments. If segments 72 (which have all socketelements) are made of a rigid balloon-expandable material and segments71 (which have all ball elements) are made of a resilient self-expandingmaterial, joints 100 may be used to facilitate crimping the assembledstent onto a balloon catheter. In particular, because ball elements 103are captured by flange 104 within socket 101, the self-expandingsegments will be compressed onto the balloon when the rigid segments arecrimped onto the balloon.

In addition, because joints 101 may be configured to provide the lockingfeature described with respect to the embodiment of FIG. 9, joints 100also may be used to lock the segments of the stent together in thedeployed configuration, thereby preventing disengagement of adjacentsegments.

An alternative embodiment of the invention is shown in FIG. 18. Thisembodiment

provides a method for assembling self-expanding medical devices that canbe customized in various ways. This alternative inter-engagement methoduses interlocking modular segments that include a rounded femaleinterface element 180, which has edges 188, and a substantiallyring-shaped male interface element 182, which has a ring 184 and twotails 186 extending off the ends of the ring at angles. These twointerface elements 180 and 182 can be coupled together, so that maleinterface element 182 projects into female interface element 180 andring 184 inter-engages in a snap fit against the underside of femaleinterface element 180. In this way, the male and female interfaceelement are held together by radial force. In this snap fitconfiguration, tails 186 of male interface element 182 bear againstedges 188 of female interface element 180. As it can be seen from FIG.18, the ring-shaped construction of male interface element 182 providesfor a lighter, more mesh-like stent than constructions, in which themale interface element is a solid disk. Further, the ring-like shape ofmale interface element 182 makes it more adaptable to engage with femaleinterface element 180, in the event that the two profiles did norexactly coincide, and also more adaptable to a shape change duringexpansion of the vascular prosthesis.

FIG. 19 shows partial side views of the inter-engagement mechanism asseen from both the proximal and distal ends of an interlocking modularsegment of this embodiment. As will be discussed in more detail herein,the circular interlocking feature ensures that the interlocking modularsegments of this embodiment do not move axially in relation to eachother and will not separate in a radial direction. FIG. 19 further showsthat rounded female interface element 180, which is part of a firstsegment 190, and ring-shaped male interface element 182, which is partof a second segment 192, have matching beveled edges, which promote therelative positioning and interlocking of the male and female interfaceelements 180 and 182 by sliding one onto the other, in contrast, forexample, with configurations in which step-shaped edges are present.

The interlocking construction depicted in FIGS. 18 and 19 not onlyenables a clinician to assemble a prosthesis of a desired length from aplurality of segments of shorter lengths, but also enables the clinicianto tailor stent properties as desired along the axial length of theprosthesis. For example, a clinician may desire to implant a prosthesishaving certain segments with higher or lower mechanical properties thanothers, in terms of tensile and compressive strength but also radialexpansion strength, longitudinal flexibility, torsional resistanceand/or resistance to foreshortening. It may also be desired to havecertain segments of the prosthesis expand at different rates or todifferent degrees than others, in order to provide a prosthesis havingsegments of different diameters after expansion, or having a generallyfrustoconical shape, or having a first segment expand faster than asecond segment, so that the locking interfaces in second segment movetowards and engage the locking interfaces in the first segment. Further,a clinician may desire to employ a prosthesis having different strutarrangements along its length, so that a prosthesis may be assembledhaving a first strut arrangements in the first segment, a second strutarrangement in the second segments, and so on.

Moreover, a prosthesis constructed according to the principles of thepresent invention may include pairs of segments that are interlocked ina substantially homogeneous manner around their circumference, and otherpairs of segments that are interlocked only along a portion of thecircumference, and/or other pairs of segments that have more male-femaleinterlocking connections along a portion of the circumference than alongthe remainder of the circumference. The last two constructions areparticularly suited for applications where the prosthesis must bepositioned at a Y-shaped, bifurcated vessel junction, more particularly,along to the leg of the “Y” and also along one of the branches of the“Y”. In this situation, the clinician arranges the prosthesis such thatthe portion of the circumference with fewer or no interlocking points isdisposed at the “Y” junction, producing a prosthesis that is has one ormore openings at the “Y” junction. For example, the prosthesis may bepositioned such to have larger cells at the “Y” junction, or to have anopening at the “Y” junction, or to develop an opening by furtherexpanding a balloon at the “Y” junction and by causing some of theinterlocking connections to open up.

FIG. 20 illustrates an interlocking modular segment 200 of the presentembodiment. Segment 200 has a proximal end 202 and a distal end 204 andincludes a plurality of struts 206 and bends 208 in an angled branchconfiguration. The network of struts 206 and bends 208 form angles wherethe struts change direction and branches where struts branch off fromeach other. As would be understood by one of ordinary skill in the art,interlocking modular segment 200 may include alternative strutconfigurations. Substantially ring-shaped male interface elements 182and rounded female interface elements 180 are formed as extensions onselected struts at the ends of segment 200. In some embodiments, thesubstantially ring-shaped male interface element 182 is disposed at theproximal end of the interlocking modular segment, and the rounded femaleinterface element 180 is disposed at the distal end of segment 200.

FIG. 21 shows an interlocking first end modular segment in accordancewith this embodiment. The first end segment 220 has a proximal end 222and a distal end 224 and includes a plurality of struts 226 and bends228. At its distal end 224, the first end segment includes a roundedfemale interface element 180. It should be noted that the first endsegment has no interface element at its proximal end 222 because as anend segment, it forms the end of an assembled medical device and doesnot require inter-engagement with other modular segments at its proximalend.

FIG. 22 shows an interlocking second end modular segment in accordancewith this embodiment. The second end segment 230 has a proximal end 232and a distal end 234 and includes a plurality of struts 236 and bends238. The second end segment includes a substantially ring-shaped maleinterface element 182 at its proximal end 232. There is no interfaceelement at the distal end of the second end segment. This is because itis an end segment that forms the end of an assembled medical device anddoes not require inter-engagement with other modular segments at itsdistal end.

Alternatively, an interlocking modular segment may have a substantiallyring-shaped interface element at each of the proximal and distal ends ofthe segment or a rounded female interface element at each of theproximal and distal ends. In other words, an interlocking modularsegment may have two male interface elements or two female interfaceelements instead of one of each. In such cases, the double male anddouble female segments would be joined to each other as the medicaldevice is assembled and alternate along the length of the device.

FIG. 23 illustrates an expanded view of a portion of a vascularprosthesis assembled with interlocking modular segments employing thesubstantially ring-shaped male interlocking element and the roundedfemale interlocking element of this embodiment. Vascular prosthesissection 240 includes a plurality of interconnected modular segments 242,which include a plurality of struts 244 and bends 246 that may bearranged in various patterns. In addition, FIG. 23 shows that thesesegments include interlocking modular segments 242, which provide theinner segments of the prosthesis, as well as interlocking first endmodular segments 248, which provide the proximal end 252 of theprosthesis, and interlocking second modular end segments 250, whichprovide the distal end 254 of the prosthesis. In accordance with theprinciples of this embodiment, inner segments 242 are interconnected bythe joining of interlocking mechanism of the ring-shaped male element180 at the proximal end of segment 242 and the rounded female element180 of segment 248. The device components can be provided to physiciansin, e.g., 5 mm components or other lengths depending on the needs of thephysician.

Toward proximal end 252 of the prosthesis, the proximal ends of theinner interlocking modular segments 242, interconnect with the distalends of the first end modular segments 248. These interconnections aremade by the substantially ring-shaped male element 182 of an innersegment 242 joining in inter-engagement with the rounded female element180 of a first end segment 248. Similarly, toward the distal end 254 ofthe prosthesis, the distal ends of the inner interlocking modularsegments 242, interconnect with the proximal ends of the second endmodular segments 250 when the rounded female element 180 of an innersegment 242 inter-engages a substantially ring-shaped male element 182of a second end segment 250. The circular interconnection mechanismensures that the different interlocking modular segments do not moveaxially relative to one another. Moreover, this mechanism together withthe super-elastic properties of the alloys used to make the interlockingmodular segments ensures that the segments do not separate in a radialdirection.

Referring to FIG. 24A, a first segment 290 and a second segment 290 and292 may be interlocked as follows. First segment 290 and second segment292 may be provided as separate elements (first step). First segment 290may then be collapsed, while second segment 292 may be left in itsoriginal condition (second step). First segment 290 may then bepositioned axially in relation to second segment 292 (third step). Firstsegment 290 may then be expanded again, for example, by removing acollapsing mechanism, interlocking first segment 290 with second segment292.

Referring now to FIG. 24B, a vascular prosthesis using the interlockingmechanism of this embodiment is shown. Vascular prosthesis 260 includesa balloon expandable material and is shown crimped in a contracteddelivery configuration over balloon 262 of balloon catheter 264. Thismay be accomplished by assembling a desired number of inner segments270, 272 between first end segments 266 and second end segments 268 toprovide a stent of a desired length, and the assembled stent may then becrimped onto balloon 262 using any of a number of previously-knowncrimping devices. Because the stent is retained centered on balloon 262,the substantially ring-shaped male interlocking elements 182 and roundedfemale interlocking elements 180 remain in engagement to form asubstantially smooth exterior surface of the stent.

Balloon catheter 262 is delivered transluminally to a target site withina patient's vessel using, for example, well-known percutaneoustechniques. Vascular prosthesis 260 or portions of the catheter may beradiopaque to facilitate positioning within the vessel. The target sitemay, for example, include a stenosed region of the vessel at which anangioplasty procedure has been conducted. In accordance with the presentinvention, inter-engagement of substantially ring-shaped maleinterlocking elements 182 and rounded female interlocking elements 180permit vascular prosthesis 260 to flex along its length to negotiatetortuous anatomy.

Alternatively, vascular prosthesis 260 may be self-expanding, that is,be manufactured from a shape memory material such as Nitinol (anickel-titanium alloy) and be caused to self-expand at the targetlocation in a vessel using techniques known in the art. Typically,vascular prosthesis 260 is disposed on a delivery catheter in acontracted state and the delivery catheter having the prosthesisdisposed thereon is covered with a sheath. The delivery catheter is theninserted into a patient's body intra-vascularly, and when the targetlocation is reached, the sheath is withdrawn allowing the prosthesis toself-expand.

When a self-expanding structure is employed, vascular prosthesis 260 maybe delivered pre-assembled (for example, by interlocking male and femaleelements mechanically, or by bonding or welding), or may be allowed toassemble in situ by delivering vascular prosthesis 260 as a plurality ofseparate segments that become interlocked during the expansion process.

Alternatively, vascular prosthesis 260 may be balloon-expandable, andthe different modular segments be delivered interlocked or may interlockduring expansion in a predetermined sequence by inflating the catheterballoon and by causing the different segments to deploy at differentspeeds and/or times.

In one embodiment of the invention, vascular prosthesis 260 is formed byone or more segments that are balloon expandable, and one or moresegments that are self-expanding. This configuration may be useful, forexample, for disposing a stent within a Y-shaped vessel branch, asdescribed in greater detail below.

Referring to FIG. 24C, balloon 262 is inflated to expand vascularprosthesis 260 to the deployed configuration in which it engages andsupports the wall of the vessel at the target site. As shown in FIG.24C, the substantially ring-shaped male interlocking elements 182continue to be retained in rounded female interlocking elements 180 whenmodular interlocking segments 270 and 272 are radially expanded. Balloon262 is then deflated and balloon catheter 264 is removed from thevessel, leaving vascular prosthesis 260 supporting the vessel. The webstructure of vascular prosthesis 260 provides sufficient radialstiffness to maintain vascular prosthesis 260 in the expandedconfiguration, with minimal recoil. Vascular prosthesis 260 optionallymay include an external coating configured to inhibit restenosis.

Turning to FIG. 25, in accordance with one aspect of the presentinvention, the segments may include different materials, strutconfigurations, wall thicknesses, and/or different types of radiallyexpandable segments that are selectively intermixed to customize thevascular prosthesis for a specific patient or application. For example,one segment may be made of a metal material and the second segment maybe made of a biodegradable material such that, after the vascularprosthesis is implanted, one segment may dissolve over time, convertingthe vascular prosthesis into a plurality of segments, for example, atthe Y-shaped branching of a bifurcated vessel. Segments also may includeside-branch apertures for use in treating bifurcated vessels, graftcovered segments for excluding aneurysms and drug-eluting segments thatare pre-loaded with a predetermined amount of drug and may be assembledto provide a desired dose. For example, whereas metallic radiallyexpandable inner segments provide increased radial stiffness in thedeployed configuration, bioabsorbable or drug-eluting radiallyexpandable segments may be better suited for drug delivery.

In the embodiment of FIG. 25, it is demonstrated how the interlockingmechanism of this embodiment can be employed to assemble a vascularprosthesis having variable traits along its length. Vascular prosthesis280 includes several relatively low radial force or strength innermodular segments which form a section of relatively low radial force,strength or rigidity 282 disposed between two relatively high radialforce, strength or rigidity sections 284 made of modular end segments ofa relatively high radial force, strength or rigidity on each end. Theinterlocking mechanism of this embodiment allows physicians to assemblethis “soft middle” stent. This configuration is useful for example, todislodge plaque from an artery. A stent of uniform radial force,including in the section to be pressed against a plaque deposit in anartery, may fail to dislodge the plaque when pressed against thedeposit.

Alternatively, because the interlocking mechanism of this embodimentincludes substantially ring-shaped male element 182 and round femaleelement 180 that are common for all segments, the segments may beassembled in any order desired for a specific patient or application.Thus, for example, the segments forming the relatively low radial forceor strength middle section 282 may be reordered so that the low radialforce segments are at one end of the stent instead of in the middle. Ofcourse, as would be appreciated by those of skill in the art, many othercombinations of materials are possible without departing from the scopeof the invention.

The embodiments depicted in FIGS. 18-25 have been described hereinbeforewith reference to a mechanical interlocking of the various segments ofthe prosthesis, by which the male and female interface elements becomemutually engaged because of the physical shapes of such interlockingelements. It should be noted, however, that the male and femaleinterlocking elements may be affixed one to the other with othertechniques as well, for example, by bonding or welding the male andfemale interlocking elements.

It should further be noted that the male and female interlockingelements depicted in

FIGS. 18-25 are shown as having only some of numerous possibleinterlocking configurations. For example, FIG. 26 illustrates anembodiment of the invention, shown in a flattened view and in a detailview, in which modular segments 300 are connected at welding zones 302and 304 in connector areas 306 that are shaped differently from theembodiments of FIGS. 18-25. A prosthesis segment having a proximal end308 and a distal end 310 includes a plurality of struts 312 and bends314, but, as would be understood by one of ordinary skill in the art,interlocking modular segment 300 may include alternative strutconfigurations. Rounded protrusions 316 are formed on selected bendsdisposed between struts. Tongs 318 are formed on different selectedbends disposed between struts. At welding zones 302, 304 the roundedprotrusion 316 on one segment joins and inter-engages with the tongs 318on an adjoining segment at a connector area 306 of the device. Thewelding zones, and ultimately the connector areas, can be formed atevery third bend, as shown in FIG. 26, or it can be at every secondbend, every fourth bend or other variations known to those of skill inthe art depending on the particular use of the medical device. An innersegment of this embodiment might have at least one welding zoneincluding a rounded protrusion at one end of the segment and at leastone welding zone including tongs at the other end of the segment.Segments that form the ends of the device would generally have at leastone welding zone including either a rounded protrusion or tongs at oneend of the segment and bends without a protrusion or tongs at the otherend of the segment. This is because end segments do not need tointer-engage with other segments at one of their ends.

Medical devices can be customized using this embodiment by mixingsegments with different material properties, e.g., austenite finishtemperatures, radial force, wall thickness or diameter, to assemble adevice with specialized configurations for specific patients orapplications. Moreover, this embodiment is particularly advantageous forproduction of long stents (e.g., 80, 100, 102 mm or longer) or stentsused in smaller areas of the body, which are becoming more common fornew applications such as critical limb ischemia or below-the-kneeapplications. This is because longer stents have a high scrap rateduring laser cutting and expansion, and the connector areas and weldingzones of this embodiment allow manufacturers to cut short segments andthen weld the device together as a cost efficient alternative totraditional manufacturing methods.

Referring now to FIG. 11, a second family of embodiments of a vascularprosthesis

constructed in accordance with the principles of the present inventionis described. Vascular prosthesis 110, for example, a stent, is showncut along line A′-A′ along its longitudinal axis and flattened into aplane for illustrative purposes. As in the first family of embodiments,vascular prosthesis 110 includes a tube-like structure made up of aplurality of interconnected modular segments, including inner segments111 and end segments 112.

Segments 111 and 112 include a plurality of struts 113 joined at theends by bends 114 to form a generally zig-zag configuration in thedeployed configuration. As would be understood by one of ordinary skillin the art, segments 111 and 112 may include many alternative strutconfigurations without departing from the scope of the presentinvention.

Referring now also to the enlarged depiction of FIG. 13, joints 115interconnect segments 111 and 112. Each joint 115 includes intertwinedspiral elements 116 and 117, wherein elements 116 and 117 have a commonorientation, either clockwise or counterclockwise, that enables theelements to intertwine Inner segments 111 include spiral elements 116and 117 at either end, while end segments 112 include such elements ononly one end. Spiral elements 116 and 117 preferably are formed asextensions on selected bends 114 disposed between struts 113 around thecircumference of the stent. Illustratively, alternating segments inFIGS. 11 and 13 are shaded for purposes of delineating the shapes ofspiral elements 116 and 117, and the segments may include the same ordifferent materials.

In FIGS. 11 and 13, spiral elements 116 are disposed on one end of eachinner segment 111 and open downwards, whereas spiral elements 117 aredisposed on the other end of the segment and open upwards. As will beapparent from inspection, the relative positions of spiral elements 116and 117 may be interchanged by flipping the segment 180 degrees relativeto the longitudinal axis of the prosthesis. Adjacent spiral elements aredepicted as having one intervening bend 114 around the circumference ofthe stent, but may include two or more intervening bends. Joints 115permit a significant degree of articulation between adjacent segments,particularly in the delivery configuration, making the stent highlyflexible and thus able to negotiate tortuous anatomy.

As noted with respect to the embodiments of FIGS. 1-10, the zig-zagconfiguration of struts 113 and bends 114 depicted in FIG. 11 preferablyis formed by laser cutting a solid tube. Vascular prosthesis 110preferably is flexible enough to conform to the shape of a delicatevessel without substantially remodeling the vessel. In particular, thezig-zag configuration of segments 111 and 112 is expected to conform toa natural curvature of a vessel wall. Of course, other patterns ofstruts and bends, such as are known in the art, advantageously be usedwithin segments 111 and 112.

Referring to FIG. 12A, vascular prosthesis 110 includes a balloonexpandable material and is shown crimped in a contracted deliveryconfiguration over balloon 120 of a balloon catheter. This may beaccomplished by assembling a desired number of inner segments 111between end segments 112 to provide a stent of a desired length, and theassembled stent may then be crimped onto balloon 120 using any of anumber of previously-known crimping devices. Because the stent isretained centered on balloon 120, spiral elements 116 and 117 remain inengagement to form a substantially smooth exterior surface of the stent.

The balloon catheter carrying the stent of FIG. 12 may be deliveredtransluminally to a target site within a patient's vessel usingwell-known techniques. Joints 115 permit vascular prosthesis 110 to flexalong its length to negotiate tortuous anatomy. Vascular prosthesis 110or portions of the catheter may be radiopaque to facilitate positioningwithin the vessel. The target site may, for example, include a stenosedregion of the vessel at which an angioplasty procedure has beenconducted.

Referring to FIG. 12B, balloon 120 is inflated to expand vascularprosthesis 110 to the deployed configuration in which it engages andsupports the wall of the vessel at the target site. As shown in FIG.12B, spiral elements 116 continue to be retained in spiral elements 117when segments 111 and 112 are radially expanded. Balloon 120 is thendeflated and the balloon catheter is removed from the vessel, leavingvascular prosthesis 110 supporting the vessel. The web structure ofvascular prosthesis 110 provides sufficient radial stiffness to maintainvascular prosthesis 110 in the expanded configuration, with minimalrecoil. Vascular prosthesis 10 optionally may include an externalcoating configured to inhibit restenosis.

As for the embodiments of FIGS. 1-10, inner segments 111 of theembodiments of FIGS. 11-13 may include different materials, strutconfigurations, or types of radially expandable segments that areselectively intermixed to customize the vascular prosthesis for aspecific patient or application. Segments also may include side-branchapertures for use in treating bifurcated vessels, graft covered segmentsfor excluding aneurysms and drug-eluting segments that are pre-loadedwith a predetermined amount of drug and may be assembled to provide adesired dose, such as described hereabove.

For example, whereas metallic radially expandable inner segments provideincreased

radial stiffness in the deployed configuration, bioabsorbable ordrug-eluting radially expandable segments may be better suited for drugdelivery. Vascular prosthesis 110 therefore may include four metallicsegments alternating with four drug-eluting segments, illustrativelycorresponding to the shaded and unshaded segments in FIG. 11.

Because joints 115 are common for all segments of the prosthesis 110,the segments

may be assembled in any order desired for a specific patient orapplication. Thus, for example, the segments may be reordered so thatthe four metallic segments are at one end of the stent, and the fourpolymeric segments are at the other end. Of course, as would beappreciated by those of skill in the art, many other combinations ofmaterials are possible without departing from the scope of theinvention.

Referring now to FIGS. 14A to 14C, a first approach to providing aradio-opaque marker on any of the prostheses of FIGS. 1-12 is described.In FIG. 14A, struts 123 (corresponding to struts 13 of FIG. 1 or struts113 of FIG. 11) are connected by bends 124 (corresponding to bends 14 ofFIG. 1 or bends 114 of FIG. 11). In accordance with this aspect of thepresent invention, selected bends 124 on either or both end segments(segment 12 in FIG. 1; segment 112 in FIG. 11) include marker housings125, in which a radiopaque marker may be disposed. Preferably, markerhousings 125 are designed such that the mechanical properties of thebend of the prosthesis are not affected. Alternatively, marker housings125 may be configured such that the marker housings function as astructural member of the prosthesis.

As shown in FIG. 14A, marker housing 125 includes aperture 126 formedtherein, wherein the aperture has a generally circular shape. As will beunderstood, aperture 126 may be formed having other shapes, such asrectangular, square, oval, octagonal, and the like. A radio-opaquemarker may be disposed within aperture 126 of marker housing 125, andmay include any material having greater radio-opacity than the materialfrom which the prosthesis is constructed. Examples of suitable materialinclude, stainless steel, gold, silver, cobalt, platinum, iridium,tantalum, and alloys thereof or similar biocompatible or bioabsorbablematerials. In a preferred embodiment, the marker includes tantalum.

As shown in FIG. 14B, the marker may be embodied in the form of rivet130 having a generally cylindrical shape and first end 131 and secondend 132. Rivet 130 may be manufactured as a composite, wherein onematerial may be radiopaque and the other material may be a therapeuticagent, e.g., a drug that elutes from the marker after implantation. Inthis case, rivet 130 may include a biocompatible material, such asdescribed above.

Still referring to FIG. 14B, first end 131 of rivet 130 may have anenlarged diameter configured to retain the rivet within aperture 126 ofmarker housing 125 prior to deformation of second end 132 of the rivet.FIG. 14C depicts marker housing 125 in which rivet 130 has been disposedand second end 132 of the rivet has been deformed to lock the rivet intoengagement with the marker housing.

Rivet 130 alternatively may be constructed of multiple pieces that maythen be assembled to form a single member when disposed within a markerhousing in accordance with the present invention. For example, the rivetmay include upper, middle, and lower pieces, wherein the middle pieceincludes means to affix the upper and lower pieces thereto, such as aprotrusion extending from each end of the middle piece, wherein theupper and lower pieces include an aperture or recessed area configuredto receive the protrusion. Alternatively, a fourth piece may be utilizedto affix the upper, middle and lower pieces together to form a marker inaccordance with the present invention.

The rivet may be manufactured from a sheet of material, wherein therivets are produced by stamping and a second process is performed toform the enlarged diameter section. Alternatively, the rivets may bemanufactured by cutting the rivets from round stock, wherein the cutportions may then be tumbled to radius the edges then machined toproduce the increased radius portion. Further still, the rivets may bemanufactured utilizing other known techniques such as injection molding,casting, machining, hydroforming and the like.

Alternatively, the marker may be integrally formed with the prosthesisdevice during manufacturing. Such a process would involve manipulating atubular member or a sheet of material from which the prosthesis isconstructed prior to the formation of the prosthesis. For example, ifthe prosthesis were to be formed from a thin-walled tubular member, agroove or other feature may be formed in one of the walls of the tube,and a radio-opaque material then disposed within the groove or feature.Alternatively, the locations of the marker housing may be pre-formed onthe device and the markers may pre-disposed within the marker housingsprior to the manufacture of the prosthesis device, which may then beconstructed according to known methods.

Referring to FIG. 15, an alternative approach to providing radio-opaquemarkers on

the prosthesis of the present invention is described. Prosthesis 140,illustratively of the type described with respect to FIG. 11, includes aplurality of markers 141 disposed along at least one of struts 142 andbends 143. Markers 141 may include rivets disposed within openingsformed in the strut members as described above or alternatively, themarkers may be integrally formed upon the strut member duringfabrication of the prosthesis.

For example, the prosthesis may be formed from a tubular member, whereinthe struts and bends are formed in the tubular member utilizing lasercutting or similar processes. Markers 141 may be formed on the struts142 and bends 143 by cutting away, machining away, chemical milling, orelectropolishing material away from the struts to form markers 141.Although markers 141 are illustratively depicted as round in FIG. 15,the markers may be formed having any shape or profile.

In FIG. 16, a further alternative approach to providing radio-opaquemarkers on the prosthesis of the present invention is described.Prosthesis 150, illustratively of the type described with respect toFIG. 11, includes a plurality of markers 151 disposed along at least oneof struts 152. Markers 151 include a clip or a band that may be attachedto struts 152, and may be constructed of a material such as tantalum,gold, gold plating, silver, silver plating, alloyed metals, polymers,plastics, or similar biocompatible or bioabsorbable materials. Markers152 may be configured to be retained on the prosthesis by deforming themarker such that the marker is frictionally retained on the prosthesis.Alternatively, markers 152 may be affixed to the prosthesis utilizingother methods such as welding, gluing, swaging, or similar methods.

It is contemplated that the markers described above may be formedanywhere along the length of the prosthesis. For example, it iscontemplated that marker housings or markers may be formed for examplein the middle of the prosthesis to indicate a specific area or propertyof the prosthesis. As such, markers may be disposed in marker housingsformed within the struts or bends of the prosthesis, or integrated inthe prosthesis anywhere along the length of the prosthesis. Furtherstill, a variety of the marker embodiments described and shown hereinmay be utilized in any combination along the length of an prosthesisaccording to the present invention, wherein different marker embodimentsmay be utilized to mark locations of interest.

Referring now to FIG. 17, an illustrative delivery system for use withthe prostheses of the present invention is described, such as describedin greater detail in International Patent Publication No. WO2004/014256. That publication is incorporated herein by reference in itsentirety. More particularly, delivery system 160 includes sheath 161 isarranged on stent 162 supported by balloon 163. Sheath 161, stent 162and balloon 163 are supported by a catheter (not shown), which may beinserted into a patient's vasculature. Sheath retraction device 164 andfluid pressure 165 are connected with the delivery system 160 by wire166 and tube 167, respectively.

Wire 164 connects sheath 161 with piston 168 in cylinder 169. Hook 170is disposed from the proximal side of piston 168. Cylinder 169 furtherincludes floating second piston 171 with opening 172 that can bepenetrated by hook 170. Floating piston 171 closes outlet 173 incylinder 169. Tube 167 connects balloon 163 with tube 174 mounted atoutlet 173 of cylinder 169. Tube 175 is connected to ainflation/deflation device schematically shown as double-arrow 176 atthe one end and via a unidirectional valve (check valve) 177 withcylinder 169 at the other end. Furthermore, tube 175 is connected via aunidirectional valve (check valve) 178 with tube 167.

Operation of delivery system 160 is as follows: Balloon 163 is in adeflated state and sheath 161 covers stent 162. Floating second piston171 is positioned so that outlet 173 of cylinder 169 and, thus tube 174,are closed. A clinician applies pressure from inflation/deflation device176 to tube 175. The pressure shuts unidirectional valve 178 and opensunidirectional valve 177. This causes pressurized fluid to flow intocylinder 169 and shifts first piston 168 in the proximal direction,thereby retracting wire 166 and sheath 161 from stent 162. The deliverysystem is designed so that the pressure required to move piston 168 isvery low.

When first piston 168 reaches floating second piston 171, the proximalend of wire 166 with hook 170 penetrates opening 172 in piston 171, andpiston 168 moves piston 171 to the proximal end of cylinder 169. Hook170 engages hook holder 179, wherein piston 168 with wire 166 and sheath161 is fixed at the proximal end. In this position, sheath 161 iscompletely retracted from stent 162, and outlet 173 of cylinder 1169 isopen. In this manner, the pressurized fluid from the inflation/deflationdevice 176 flows via tube 175 and the left side of cylinder 169 throughoutlet 173, tube 174 and tube 167 to balloon 163, and inflates theballoon to deploy stent 162. The pressure may be applied until a desiredexpanded diameter is attained for the prosthesis.

Once the prosthesis is deployed, the clinician applies a vacuum from theinflation/deflation device 176 via unidirectional valve 178 and tube 166to balloon 163. During this suction step, unidirectional valve 177 isclosed. At the end of the stent delivery and deployment process, thecatheter with balloon 163 and sheath 161 is removed from the patient'svessel, leaving the prosthesis in the desired position within thevessel.

It is to be understood that the foregoing delivery system is merelyillustrative of the types of delivery systems that may be used todeliver and deploy the prostheses of the present invention.Alternatively, a delivery system such as described in co-pending,commonly assigned U.S. patent application Ser. No. 10/932,964, filedSep. 2, 2004, and entitled “Delivery System for a Medical Device,” whichis incorporated herein by reference, may be employed

It should be understood that any of the foregoing joint configurationsand specialized modular segments may be interchangeably used with any ofthe vascular prostheses of the preceding embodiments. In this manner,the methods and apparatus of the present invention permit a vascularprosthesis to be tailored to a given patients anatomy or a specificapplication.

Although preferred illustrative embodiments of the present invention aredescribed

hereinabove, it will be evident to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. It is intended in the appended claims to cover all suchchanges and modifications that fall within the true spirit and scope ofthe invention.

1. A method of assembling a modular prosthesis comprising: providing oneor more interlocking modular segments, wherein each interlocking modularsegment has a proximal and a distal end, a plurality of struts and aplurality of bends disposed between the proximal and distal ends, a ringshaped male interface element at the proximal end of the module, and arounded female interface element at the distal end of the module; andjoining the one or more interlocking modular segments by inserting thering shaped male interface element at the proximal end of a firstinterlocking modular segment into the rounded female interface elementat the distal end of a second interlocking modular segment providing aplurality of interlocking modular segments in addition to the first andsecond interlocking modular segments; and joining the additionalinterlocking modular segments by inserting the ring shaped maleinterface element at the proximal end of one or more interlockingmodular segments into the rounded female interface element at the distalend of another one or more interlocking modular segments, therebycausing a plurality of interlocking modular segments to extend from theproximal end of the first interlocking modular segment, and a pluralityof interlocking modular segments to extend from the distal end of thesecond interlocking modular segment.
 2. A method for assembling avascular prosthesis comprising: providing at least a first modularsegment and a second modular segment wherein each modular segment has aproximal and a distal end, wherein each modular segment further has aplurality of struts and a plurality of bends, wherein the first modularsegment has at least one welding zone comprising a rounded protrusionformed on at least one selected bend, wherein the second modular segmenthas at least one welding zone comprising tongs formed on at least oneselected bend, and welding the at least one welding zone of the firstmodular segment to the at least one welding zone of the second modularsegment to form at least one connector area where the first modularsegment and the second modular inter-engage.
 3. The method of claim 2,further comprising: forming a welding zone at every third bend of thefirst modular segment and forming a welding zone at every third bend ofthe second modular segment; and welding the welding zone at every thirdbend of the first modular segment to the welding zone at every thirdbend of the second modular segment to form a connector area where everythird bend of each of the first modular segment and the second modularsegment inter-engage.
 4. The method of claim 2, wherein the firstmodular segment further comprises at least one welding zone comprisingtongs formed on at least one selected bend, and wherein the secondmodular segment further has at least one welding zone comprising arounded protrusion formed on at least one selected bend.